Is masser today a must? and if yeah how much percent, is there a difference between in Eretz Yisrael and chutz la’eretz??
Maaser today is a must. The amount that is seperated in practice is little more than 1% of the produce. The reason it is a little more than a percent is because terumas maaser is 1 percent, and teruma is even a drop, therfore it comes out a drop more than 1%. We only have to sperate terumos umaaseros from produce that was grown in Eretz Yisroel, however it doesn’t matter where the produce in eaten. Therefore produce from Israel eaten in the USA still has to have terumos umaasros seperated from it before eating.
For giudance on how to seprate terumos u’maasros please see the following links https://dinonline.org/2017/07/26/how-do-i-take-terumah-and-maaser-from-israeli-vegetables/ and https://dinonline.org/2020/11/21/fruit-tithe-outside-israel/ Best wishes